Starting and operating unit and circuit for gaseous electric discharge devices



y 1948- M. A. BABB ET AL 2,445,989

STARTING AND OPERATING UNIT AND CIRCUIT FOR GASEOUS ELECTRIC DISCHARGEDEVICES Filed May 22, 1945 Y s Sheets-Sheet 1 ATTORNEYS M. A. BABB ET AL2,445,989 STARTING AND OPERATING UNIT AND CIRCUIT FOR July 27, 1948.

GASEOUS ELECTRIC DISCHARGE DEVICES 5 Sheets-Sheet 2 Fiied May 22, 1945 Ar l INVENTOR MaynardAiBabb Arnold l? Hayes BY 7 9w4 ATTORNEYS July 27,1948.

M. A. BABB ET AL STARTING AND OPERATING UNIT AND CIRCUIT FOR.

GASEOUS. ELECTRIC DISCHARGE DEVICES Filed May 22, 1945 3 Sheets-Sheet 3INVENTOR 2910122! I]. Hayes ATTORNEYS Patented Jul 27, 1948 CIRCUIT FORGASEOUS ELECTRIC DISCHARGE DEVICES Maynard A. Babb, Elkins Park, andArnold E.

,Hayes, Philadelphia la assignors toMaxwell M. Bilofsky, Newark, N. J.

Application May 22, 1945, Serial No. 595,212

The present invention is concerned withsafety starting units and withcircuits incorporating the same, for the protection of gaseouselectrical discharge devices such as fluorescent lamps of the hotcathode type. i

It is among the objects of the invention to provide a unit of the abovetype, which is compact and relatively inexpensive, which lends itselffor use with fluorescent lamps and the conventional fixtures thereof, asa replacement for glow starters of conventional type and in which inherecertain added utilities, including the prompt elimination of theintermittent flashing on and off of a defective lamp and thereby notonly avoiding the annoyance of such flashing" but also safeguarding thestarter unit itself from the destructive strain imposed thereon by suchintermittent starting. i u

Another object is to provide a starter unit of the above type, thesafety circuit of which operates dependably, promptly to preclude theapplication of starting current to a defective lamp and reliably tomaintain the lamp from flashing,

and automatically restores itself to permit normal operation of a newlamp when substituted for the defective one.

Another object is to provide a safety starter circuit and unit of theabove type which, in the normal operation of the lamp, involves not the,

slightest use of power or current beyond what is consumed in theoperation of the same lamp in the absence of the safety feature.

A feature of the invention is a switch arm in series with theconventional starting contacts in the starting connection between theelectrodes of a gaseous electric discharge device, said switch arm beingdisplaced in response to the prolonged starting current in the attemptedstarting of a defective lamp and being maintained in displaced positionby current operated means that is connected into circuit by thedisplacement of the switch arm. In the preferred embodiments shown, theswitch is heat responsive and is actuated by the heat evolved in aresistor through which the starting current flows and when in displacedposition connects into circuit a second 12 Claims. (01. 315-100) Fig. 2is a similar view of an a1ternativeform of circuit, H Fig. 3 is a viewshowing the casing in longitudinal cross section of the front elevationof one embodiment of glow starter unit incorporating the circuit of Fig.1,

Fig. 4 is a view similar to Fig. 3 showing a side elevation, 1

Fig. 5 is a view in transverse cross-section taken on line 5-5 of Fig.4,

Fig. 6 is a view similar to Fig. 3 showinga rear elevation, i i f L f.

Fig. 7 is a fragmentaryperspective detail, view.

. Fig. 8 is a detail sectional view of the composite resistor unit, i

Fig. 9 is a fragmentary circuit diagram; of. a modification, and:

Fig. 10 is a view similar to modification.

Referring now to the drawings, there is shown in the diagrammatic viewof Fig. 1, a conventional gaseous electric discharge device In of theFig. 9 of another hotcathode type, such as a fluorescent lamp ineludinga pair of electrodes Hand l2 at opposite ends thereof. One of the mainsl3 hasthe.

ballast coil [4 therein, and the main switch is shown in the other main[6. The startingcircuit between said electrodesincludes aconventionalstarter ll of the thermal, magnetic or, glow switch type. InFig. 1 the glow switch type of starter is illustratively shown, thecontacts 18 and I9, one of which is carried by a binietal strip 20, areshunted by a condenser 2| to minimize arcing.

The starting current passes across the open gap between the contacts I8and I9 and the heat of the glow discharge therebetween causes thebimetal strip 20t0 deflect and close the gap, so that the full voltageis applied-through the lamp electrodes I] and I2, in series, whereuponthe bimetal strip 20 cools and the gap reopens to permit a surge fromballast coil M to strike the arc in the lamp, or the cycle repeats untilsuch are is actually struck, whereupon the glow switch remains open. Thecontacts, thus separatedto effect starting of the. lamp will bedesignatedthe starting contacts.

According to the present invention, there is connected in, the seriescircuit across the .electrodes ll and IZ and in series with starter- Ila thermally responsive time delay'switcharm 22 bearing a contact23engaging andclosingcircuit to contact 24 in lead 25 from the starterswitch l'l. These contacts will be designatedthe safety contacts. Thetime delay switch is de- According to the invention, a second resistor28, normally out of circuit.is connected tothe,

under the repeated abortive starting operations, and this would deflectthe safety bimetal switch 36 away from contact 3'! toward contact 38,thereby cutting into circuit an auxiliary resistor 38 adjacent thesafety switch 3%, and connected by lead 0 electrode 35. Once the safetyswitch 36 has operated after the initial abortive starting impulses upona defective lamp, the current will pass .from main 35 through resistor34, electrode 36,

electrode H and has a contactIl29 ..in thepa'th of deflection of switcharm 22, said resisto128 being also arranged relative-to said arm 22 tomaintain the same heated whenever saidr'si'stor is in circuit.

In operation, when the main switch i5 is closed, I the current will flowthrough electrode l-l through glow switch ll, lead 25, contacts 24 and23, thermally responsive switch arm 22, resistor 26 and lead 21 to thecompanion electrode 12. With a ""riorr'nallyoperativelamp, 'whenthearcstruck -the glow switch ll will be open, interrupting the'series'""corfnectionbetween electrodes l I and i2 "andaslon'g"as"the"arc is" maintained, said switch remains open.

Should the lamp be defective and be'incapable of maintainin'gthe are buttend toflash' on and 01f intermittently, the bimetal switch-22 will be-"'come excessively "heated by the heat evolved in resistor 26, after a'f'ew'pf sucliabortivestarting the otherielectrode 3 i 39' combined withthat of starting resistor 34, the

starter switch 32, contact 33, lead ti, safety switch 35, contactresistor 33 and lead A?! to Under the heat of resistor safety switch 36stays in deflected position as long as the circuit remains closed.Resistor 39 cuts down thecurrent in the safety circuit to such an extentthat no arcing can occur across electrodes 30 andt I.

-In-Figs. 3 to '7, inclusive, is shown a desirable glow starter unitincorporating starting and safety controls of thecircuit shown in Fig.1, al-

though obviously a similardevicemayre'adily be devised to incorporatethe starting"and'*safety controls-of the circuit of Fig. 2.Therefer'ence numerals in the circuit of Fig. 1 'will'be used todesignate the corresponding elements'of 'the structure of Figs. 3 to 7.The'unit'involves the conventional"insulating base 50 withitstwo'terminal DGStSfEi and Hand with a metal cap 53 having tabsfid tosecure it to the base 59.

The cap 53 "has insulating lining55 1 covering its side wall and furtherinsulating lining- 55 for its top wall. In the unit is enclosed theinsulating upstanding panel-56 afiixedwith .35 respect to one of theterminal posts-5i to one side of which is mounted the glowstarter-switch ll. 7 That switch may be of conventional constructioninvolving a neon-filled glass tube "5? with electrodes 251, one of whichis U-shap'edand of'bimetal. The control devices are disposed at the sideof the panel 56 opposed to theglow'tube Ill. The bimetal switch 22preferably in the form of a leaf, is aihxed as by welding one endt'hereof'to a finger 58 on a metal c1ip'59 riveted as at fill to thepanel 56 and preferabl upset at one end 61 into the panel to precluderotary shifting of the clip about the rivet. The bimetal leaf 22 extendsupward the length of the panel and has a wire contact 23 at its end,which engages a wirecontact 24 spaced from the panel 56 and mounted on aclip 62 afiixed as by rivet'tfi to the upper end of thepanel 56, therear of said rivet 63 being connected to one'of the terminal leadsfii ofthe glow discharge tube.

'The lower end of the bimetal switch 22 passes in aloop 22 aboutresistor R. That resistor (Fig. 8) has an electricallyresistingcoreelement28 desirably of carbon or metal composition, "oneterminal wire 65 of which is soldered as at 66 to the panel 56 andconnected to terminal post 5| to which is connected the other terminallead 69 of the glow discharge tube ll. The opposite terminalwire 68 ofthe carbon resistorextends upward along panel 56 to a clip it riveted atH and soldered to the upper end of the panel and connected to a wirecontact member 29 near contact 24 and normally spaced from the wire end-23 of the bimetal switch 22.

Coiled about the composition resistor'28 is a wire resistor 26 desirablyof Nichrome wire. One terminal of this resistor 26 extends through theaperture 12 in the panel 56 to the terminal post 52 inthe base 50 andthe oppositeend'lt of said wire resistor26 extends through the rivet 75"60 and is soldered to the clip 59.

""operat'ions'h'ave taken "place. As 'a consequence, the bimetal switch22 will open the series circuit "at' contact '2 i' and willengagecontact 29,- so that 'the circuitnow will be from-electrode I Ithrough resistor 28, contacts 29, bimetal switch arm 22, resistor-2 6andlead' 2'! to the "companionelectrode 12. The resistor 28 is ofresistance so high'that "thes'eries connection now established acrossthe electrodes l I and !2 cuts down the-current to "'negligible'values.The heat evolved by thetwo resistors 25 and 28' inseriesywhichareadjacent thebimetal' "switclfarm 22, is "sufficiently intense 'tbkeepsaidarrhin the-deflected position against contact 29 andtherebytopreclude flashin of the tl'ai'np' as long as the main switch l5remains Nosed. When saidswitch l 5" is opened, the'bi-"r'netalswitchjarmfl returns'byits naturalbias to"thepos'ition"shownin"Fig; 1,"so that the circuit automatically returns"to" its "normal position to "*pr'ot'ect "a new. orreplacement lamp andwithout needfor inanual'resetting. If the defective lampis"not"replaced; itwi'll flash onand' elf-through a "f'ew 'cycles'whenever the main" switch is again closed, to apprise of the need forreplacement, but will then"remain"dark'- as above set forth.

InFig'. 2 is shown the application'of the circuit "'to a'thermal'type ofstarter; in which the'series starting'connection between the electrodes30 and 3 Viricludes' the bimetal switch arm 32 normally "closed -againstcontact-33 andadapted to open by the time the lamp" has arced over inthe "ordinary "foperationof a perfectlamp under themoderate "heatevolved in' an "adjacentresistor 34 iri'circuit "betweenthemain"35andthe electrode 30. According to the present invention; there is con-"""nected 'in' series with the bimetal starter switch 32, by way of leadM, a bimetal safety switch 36 orma11 clos'ed'against contact-'51. Thissafety "switch'is'also" subjected to the heat evolved in resistor"34,but is less sensitive than the normal Tstarter switcli'32so"that"it"'will not become deflect'ed'infthe'normal operation' of aperfect lamp. Inthe'operation of a-defectivelamp, however,'-"'exces'sive heat would be evolved" in resistor" 34 The wire resistoris preferably combined in a unitary structure with the compositionresistor by embedding said wire in a coating of suitable resin orporcelain cement i l. The loop 22' of the bimetal switch is spaced fromthe composite resistor R by a gap in the order of .01 inch.

It will be understood that the set of the bimetal switch 22 isdetermined so as to efiect the desired safety operation, whether thelamp is being used in a cold or in a hot environment. To this end thespring tension is such as to maintain the contact against contact 24even at the highest temperature encountered in use of the operativelamp.

, Preliminary to the operation of the safety switch, the resistor 26will preheat the composition resistor 28 encompassed thereby so that thecomposition resistor 28 will reach the correct temperature for mosteffective operation in aiding the deflection of bimetal switch 22 fromcontact 24 to contact 20.

The spacing of the contacts 29 and 24 is the minimum consistent with noarcing and in practice is preferably equal to the diameter of contactwire 23 plus about .010 inch. By reason of the preheating of resistor 28and the heat storing ability of'the resistor assembly of Fig. 8, theresistor temperature remains considerably higher than that of thebimetal leaf 22 and therefore the movement of contact 23 on leaf 22 from24 to 29 occurs quickly.

The heat generated by the resistor 26, 28 (Fig. 8) is of the orderrequired to maintain the closure of the safety circuit even at thelowest voltage or temperature encountered.

In practice the composition resistor 28 which is normally out ofcircuit, may be of resistance of the order of 20,000 ohms, while thewire resistor 26 which is in circuit during the starting operation of anormal lamp may be of resistance of the order of 10 ohms.

As is clear from the foregoing, the resistor 28 or 39 of Figs. 1 and 2respectively, and which is normally disconnected, is switched intocircuit by the deflection of the safety switch under the action ofresistors or 34 respectively, in abnormal operation and serves to holdsaid switch against return from such deflected position.

While in Figs. 1 and 2, the two resistors are connected in series toprevent continued flashing of a defective lamp, it will be understoodthat the single holdout resistor 23 or 39 respectively, would alone beeffective for the purpose, even though the actuating resistor 26 or 34respectively, be cut out of circuit the instant it has performed itsfunction of switching the hold-out resistor into circuit.

In Fig.9 is shown an arrangement for thus switching a hold-out resistorinto circuit and concomitantly switching the actuating resistor out ofcircuit. The actuating resistor 16 connected to one terminal of thestarter switch ll is connected directly to the hold-out resistor 18which is normally out of circuit, since itsother terminal is connectedto the normally open contact 19 in the path of deflection of safetyswitch 80. The electrode 8d of the lamp is connected in the main 83, andopposite electrode 85 in the main 8i at the supply side of resistors l5and 1B. Preferably the two resistors l6 and i8 are closely juxtaposed,substantially as in Fig. 8.

In the normal starting operation, the current passes from main 8!through electrode 85 to resistor lli and thence through the starterswitch 11, contact 82, and safety switchBllby way of electrode 84 to theother main 83. Upon excessive heating :of resistor 16 as a result of theabortive attempts to start a defective lamp, the safety switchdisengages contact 82, and closes on contact 19, where it is held by theheat evolved in resistor 18, which is now connected in series withsafety switch 80 and with electrodes 84 and 85 across the mains BI and83, the companion resistor 16 bein now out of circuit.

In Fig. 10 is shown an arrangement generally similar to that of Fig. 9except that the actuating resistor 76 intervenes between the electrode85 and the connector 86 extending from the junction between theactuating resistor 76' and the holdout resistor 18. Accordingly in thenormal start ing operation, resistor i8 is out of circuit, but upondeflection of safety switch at under the in fiuence of the heatgenerated by actuating resistor 16 in attempting to start a defectivelamp, the circuit passes from main 83' through electrode as and safetyswitch 80' through resistor it and it in series to electrode 35 and theother main 3!.

The circuit of Fig. 1, as above described, lends itself readily toincorporation of the entire con trcl equipment including the starter,the thermal switch arm and the associated resistors in a single unit, asshown in Figs. 3 to '7, which has but two terminals connected to theelectrodes of the lamp. Likewise the entire control equipment of thecircuit of Fig. 9, and that of Fig. 10 as Well, can be incorporated in asingle unit with but two termi nals connected to the electrodes of thelamp. The control equipment of the unit of Fig. 2 can be similarlyincorporated, except that it requires more terminals.

As many changes could be made in the above construction, and manyapparently widely differ ent embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained inthe above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having thus described our invention, what we I claim as new and desireto secure by Letters Patent of the United States is:

l. A safety starting and operating circuit for a gaseous electricdischarge device equipped. with spaced electrodes, said circuitcomprising a starting connection including a pair of starting con.-tacts, a pair of safety contacts and a heating element in series, withone of said starting contacts being connected directly to one of saidsafety contacts, whereby when said starting connection is in series withsaid electrodes and a sou-roe of current, current will pass through saidstarting connection and said electrodes, actuating means in series withsaid starting contacts controlled by current flow through said startingconnection, separating said starting contacts and maintaining the latterseparated only while the arc of the electric discharge device ismaintained, thermally responsive, electrically conductive, displaceablemeans actuating at least one of said safety contacts and responsive tothe prolonged starting current through said heating element in the attempted operation of a defective electric discharge device forseparation of said safety contacts, and current operated heat evolvingmeans positioned adjacent said displaceable means, directly connected atone end to the other of said starting contacts, having its free endnormally disconnected from said safety contacts, and in the path ofmovement of said displaceable means, whereby upon separation of saidsafety; contact's, an.d en:-

7 gag'ment-of said dis'placeable means with said free end, said "currentoperated heat evolving means will be connected'in series with saidtwoelectrodes, said heating element and such source of-c'ur-rentto'maintain said safety contacts separated; I

2. The combination set forth in claim 1 in which the end of said currentoperated heat evolving means connected to the other of said startingcontacts is also directly connected to one of such electrodes;

3. The combinationset forth in claim 1 in which the-end of said currentoperated heat evolving means connected to the other of said startingcontacts is also directly connected to said heating element.

4. A safety starting and operating circuit for a gaseous electricdischarge device equipped with spaced electrodes, said circuitcomprising a starting connection including a pair of normallyengagedstarting contacts, a pair of safety contacts, a resistor and a heatresponsive electrically conductive safety switch arm in series, saidresistor being in thermal association with said switch arm, with one ofsaid starting contacts being connected directly to one of said safetycontacts and said switch arm carrying the other of said safety contacts,whereby when said starting connection is in series with said electrodesand a source of current, current will pass through said startingconnection and said electrodes, actuating means in series withsaidstarting contact controlled by current flow through said startingconnection, separating said starting contacts and maintaining the latterseparated only while the arc of the electric discharge device ismaintained, said resistor evolving sufficient heat in the attemptedoperation of a defective electric discharge device for displacement ofsaid safety switch arm and separation of said safety contacts, and asecond resistor in thermal association with said switch arm, normallyout of circuit, directly connected at one end to the other of saidstarting contacts and having its free end normally disconnected fromsaid switch arm and in the pathof movement of the latter, whereby upondisplacement of said switch aurn and engagement with said free end, saidtwo resistors and said switch arm will be connected in series with saidtwo electrodes and such source of current, said two-resistors conjointlygenerating sufiicient heat to maintain the switch arm in deflectedposition against said free end as long as the circuit is closed.

5. A safety starting and operating circuit for a gaseous electricdischarge device equipped with spaced electrodes, said circuitcomprising a starting connection including a pair of safety contacts, aheating element and a glow switch starter having a pair of startingcontacts, all in series, with one of said starting contacts beingconnected directly to one of said safety contacts, whereby when saidstarting connection is in series with said electrodes and a source ofcurrent, current will pass through said starting connection and saidelectrodes; said pair of starting contacts in said glow switch starterseparating and remaining separated only while the arc of the lamp ismaintained, a heat responsive electri cally conductive safety switch armactuating at least one of said safety contacts and responsive to ftheprolonged starting current through said heatingelement in the attemptedoperation'of a defective lamp for separation of said safety contacts;and a second heating element positioned adjacent said switch arm,directly connected at one end to the" other of said'startmgcontacts, andhavingits free end normally "disconnected from said safety contacts, andin the path of movement of said'switch' arm, whereby upon separationofsaid safety contacts and engagement of said switch arm'with said freeend; said two heating elements will be connected in series with saidtwo' electrodes, said two heating elements conjointly generatingsufficient heat to maintain -said switch arm in deflected positionagainst said free end as long as the'circuit is closed.

6. A safety starting and operatingcircuit'for a gaseous electricdischarge device equipped with spaced electrodes, said circuitcomprising a starting connection including a pair of normally openstarting contacts, a pair of normally closed safety contacts, a resistorand a heat responsive electrically conductive safety switch arm"carryingone of said safety contacts, all in series with one of said startingcontacts being connected directly to the other of said safety contacts,whereby when said starting connection is in series with said electrodesand a source of current, current will pass through said startingconnection and said electrodes, actuating means in" series with saidstarting contactscontrolling the latter and controlled by current'fiowthrough said startingconnection, said actuating means being normallyinoperative while the 'arc of the electric discharge device ismaintained, whereby said'starting'contacts will be retained inopenpositionto break the circuit from such source of current to saidresistor, said resistor evolving sufficient heat in the attemptedoperation of a defective electric discharge device for displacementofsaid safety switch arm to separate said safetycontacts, and a secondresistor'in thermal association with said switch arm directlyconnected-at one end-to the other of said starting contacts and havingits free end normally disconnected from'said switch arm and in the pathof movement of the latter, whereby upon displacement of said switch armand engagement with said free end, said two resistors and said switcharm will be connected in series with said two electrodes and such sourceof current, said two resistors conjointly generating sufiicient heat tomaintain the switch arm in deflected position against said free endaslong as the circuit is closed.

'7. A safety starter for a gaseous electric discharge device equippedwith spaced electrodes, said starter comprising a starter unit includinga pair of starting contacts, means for actuating said contactsrepeatedly to open and close the latter, an associated bimetalsafetyswitch arm, a support "therefor at one endthereof', a pair ofresistances at the support end of said switch arm in heat transferrelation thereto, a pair'of neighboring contacts, one of saidneighboring contacts being connected t'oone of said starting contactsand normally engaged bythe free end of said switch arm, the other ofsaidneighboring contacts being normally spaced'from'the free end of saidswitch arm in the path of movement thereof and connected to one end ofone of said resistances; the free' endof said last named resistancebeing connected directly to the other of said starting contacts, a pairof terminals, one of said terminals being connected to one end of theother of said resistances, the other end of said last named resistancebeing connected in series with said safety switcharmysaid pair" ofstarting contacts," and said other terminal.

8. A safety start'erfor'a gaseous"electricdischarge device "equippedwith spaced electrodes,

said starter comprising a starter unit including a pair of startingcontacts, means for actuating said contacts respectively to open andclose the latter and to leave them open upon initiation of a dischargebetween said electrodes, an associated bimetal safety switch arm, asupport therefor at one end thereof, a pair of resistances at thesupport end of said switch arm in heat transfer relation thereto, one ofsaid resistances being connected at one end to said bimetal switch arm,a pair of neighboring contacts, one of said neighboring contacts beingconnected to one of said starting contacts and normally engaged by thefree end of said switch arm, the other of said neighboring contactsbeing normally spaced from said switch arm and connected to one end ofthe other of said resistances, the free end of said last namedresistance being connected directly to the other of said startingcontacts and a pair of terminals connected respectively to said lastnamed starting contact and the free end of said first named resistance.

9. A safety starting device for a gaseous electric discharge lampequipped with spaced electrodes, said device comprising a self containedunit including a starter element having a pair of starting contacts,means for actuating said contacts repeatedly to open and close thelatter and to leave them open upon initiation of a discharge betweensaid electrodes, 9, safety element comprising a bimetal switch leaf,said switch leaf having a loop at one end affixed to said panel, and acontact carried by the other end thereof, a heater unit encompassed bysaid loop of said bimetal switch leaf, said heater unit comprising apair of heater elements in heat transfer relation to said switch leaf,one of said heater elements being connected at one end to said switchleaf near the looped end thereof, a terminal post connected to the otherend of said heater element, a pair of fixed contacts mounted on thepanel adjacent the contact carrying end of said switch leaf, one of saidfixed contacts being connected to one of said starting contacts andnormally engaged by the contact carried by said switch leaf, the otherof said contacts being normally spaced from said contact carried by saidswitch leaf and connected to one end of the other of said resistances,the free end of said last named resistance being connected directly tothe other of said starting contacts and to a second terminal post.

10. The combination set forth in claim 9 in which said first resistorencompasses said second resistor.

11. In a safety starter unit, th combination of a support base, a panelrising therefrom, a starter element at one side of the panel andincluding a pair of starting contacts, means for actuating said contactsrepeatedly to open and close the latter, and safety means at the otherside of the panel, said safety means comprising a bimetal switch armhaving a looped portion at on end affixed to said panel, a contact atthe free end of said bimetal switch arm, a pair of neighboring contactsincluding a, contact normally engaged by said switch contact andconnected to one of said starting contacts, and a second contactnormally spaced from said switch contact, a resistor unit disposed inthe bight of said loop and in heat transfer relation to said switch arm,said resistor unit including a composition resistance connected at oneend to said second contact, and a wire resistor connected at one end tosaid bimetal switch arm, and a pair of terminal posts through saidsupport base and connected respectively to the other end of said wireresistor, and to the other end of said composition resistor and to theother of said starting contacts.

12. A safety starter unit for a gaseous electrical discharge device,comprising a support base having a pair of terminal posts, an insulatingpanel rising therefrom, a glow switch starting unit mounted on one faceof said panel and including a pair of normally open starting contactshaving one of said starting contacts connected to one of said posts,safety means mounted on the other face of said panel, said means in.said glow switch starting unit for actuating said contacts repeatedly toopen and close the latter, safety means comprising a bimetal switchhaving a loop at its base and affixed to said panel, a resistor unitdisposed in the bight of said. loop and comprising a compositionresistance, a lead from said resistance extending along said panel, anda contact extending transversely at the top of said panel and connectedto said lead, the opposite end of said composition resistor beingconnected to said last named terminal post, said resister unit alsoincluding a wire resistor, one end of said wire resistor being connectedto said bimetal switch, the other end of said wire resistor beingconnected to the other terminal post, said A panel having a contact nearbut spaced from said transverse contact and normally engaged by theouter end of said bimetal switch, said latter contact being connected tothe other starting contact of the starter unit.

MAYNARD A. BABB. ARNOLD E, HAYES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,788,970 Andre et a1 Jan. 13,1931 2,160,823 Black June 6, 1939 2,285,450 McCarthy (a) June 9, 19422,294,191 Lord Aug. 25, 1942 2,299,499 Sanford Oct. 20, 1942 2,333,215Thomas Nov. 2, 1943 2,341,520 Babb Feb. 15', 1944 2,343,262 McCarthy (b)Mar. 7,1944 2,344,774 Hodgkins Mar. 21, 1944 2,379,115 Thayer June 26,1945 2,408,093 Patterson Sept, 24, 1946

